Require project link in #open-source-contributions

[crimson spindle]

The post guidelines in #981642226927009792 don't mention including a link to the project. I think this should be in the minimum requirements for posting there, and also a good idea because people will want to look at your source

thought of this when reading https://discord.com/channels/273534239310479360/1453167770026901554 which is prrrrobably a job ad and not a project

[kindred orbit]

added, thanks for the suggestion